Chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} at rates of 140 g ai/ha and lower did not reduce wheat (Triticum aestivum L. 'Stephens’) grain yield, but soil residues from 35 g/ha injured snap beans (Phaseolus vulgaris L.), alfalfa (Medicago sativa L. ‘DuPuits’), sweet corn (Zea mays L. ‘Jubilee’), Italian ryegrass (Lolium multiflorum Lam.), sugarbeets (Beta vulgaris L. ‘Giant Western’), and rape (Brassica napus L. ‘Dwarf Essex’). Chlorsulfuron at 35 g/ha reduced foliage weight of sugarbeets seeded 26 months after application. Phytotoxic levels of the herbicide were present 10 to 20 cm deep, 168 days after application to a silt loam soil. Chlorsulfuron reduced alfalfa petiole length and fresh weight in the greenhouse when mixed in soil at rates as low as 0.025 ppb (w/w).

Live root material of leafy spurge (Euphorbia spp.) was collected from 38 locations across northern United States, southern Canada, and from 1 location in Austria. These materials were established in a nursery at Lincoln, Nebraska along with E. agraria M. Bieb. and E. cyparissias L. # EPHCY. Nineteen vegetative and reproductive characters, taken from various taxonomic keys, were measured on plants established for a period of 3 yr. Data were compared with previous taxonomic keys of Euphorbia species. A key developed by A. Radcliffe-Smith was used to separate the nursery entries. Leaf width measurements were the most useful taxonomic criteria. Five morphologically separable taxa were observed: E. × pseudovirgata (Schur) Soó, E. esula L. # EPHES, E. uralensis Fisch. ex Link., E. agraria M. Bieb., and E. cyparissias L.

Thirteen-day-old common cocklebur (Xanthium pensylvanicum Wallr. # XANPE) plants were treated with 15 μg glyphosate [N-(phosphonomethyl)glycine] applied to the lowermost true leaves. Growth was inhibited rapidly following treatment. About 56% of applied 14C-glyphosate was taken up within 8 h. Within 4 days after treatment, diffusive resistance increased in treated leaves but did not change in untreated leaves. Glyphosate had little effect on nonstructural carbohydrate content of leaves, but soluble carbohydrate levels of stems and roots had increased by 130 and 180%, respectively, by 56 h after treatment. The uptake of 33P into roots was unaffected by the herbicide, but transport of P to the aerial tissues was severely inhibited. Effects such as inhibition of P movement could result from inhibition of protein synthesis.

The influence of buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone}, diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] on fluorescence emission and post-luminescence decay in chlorella (Chlorella vulgaris Beyer) was studied. All three herbicides blocked photosynthetic electron transport and thus enhanced fluorescence. Buthidazole was the most active, a 79% increase in fluorescence being observed when algal cultures were exposed to 1 × 10-6 M herbicide for 5 min, and a 206% increase with an exposure time of 60 min. Postluminescence in chlorella exposed to 1 × 10-6 M buthidazole for 5, 10, 20, and 60 min was inhibited 15, 34, 58, and 69%, respectively. Diuron and atrazine inhibition of postluminescence was much less than that of buthidazole. The ratio of relative fluorescence to relative postluminescence can be sued to give a numerical value (C) for the phytotoxicity of this type of herbicide to a given plant species.

Tank mixtures of herbicides for control of emerged winter weeds and preemergence control of large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] were evaluated on bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’ # CYNDA] fairways over a 2-yr period. Glyphosate [N-(phosphonomethyl)glycine] applied at 0.28 kg ai/ha in tank mixtures with DCPA (dimethyl tetrachloroterephthate) at 11 kg ai/ha controlled a higher percentage of parsley-piert (Alchemilla microcarpa Boiss. Reut. # APHMI) than either herbicide alone. When applied for spur weed (Soliva spp.) control, DCPA was antagonistic in the tank mixture with simazine [2-chloro-4,6-bis(ethylamino)-s-txiazine]. During one yr of the 2-yr study period, control of large crabgrass was less in plots treated with combination of DCPA and glyphosate than in plots treated with DCPA alone. Less large crabgrass control was obtained in plots treated with bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] at 11 kg ai/ha in combinations with either paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) or 2,4-D [(2,4-dichlorophenoxy)acetic acid] plus mecoprop {2-[(4-chloro-o-tolyl)oxy]propionic acid} plus dicamba (3,6-dichloro-o-anisic acid) than when treated only with bensulide.

Field experiments were conducted for 2 yr to determine the influence of picloram (4-amino-3,5,6-trichloropicolinic acid) and a commercial mixture of picloram plus 2,4-D [(2,4-dichlorophenoxy)acetic acid] (1:16, w/w) on control of wild oats (Avena fatua L. # AVEFA) with four postemergence herbicides. The phytotoxicity to wild oats of barban (4-chloro-2-butynyl m-chlorocarbanilate) or difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) in 1981 and diclofop {2-[4-(2,4-dichlorophenoxy)-phenoxy] propanoic acid} or flamprop [N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL-alanine] in 1981 and 1982 was reduced when these herbicides were applied in a mixture with picloram plus 2,4-D. Consequently, the use of these mixtures for broad-spectrum weed control in one spray operation is not recommended. Picloram applied at a rate equivalent to the amount present in the picloram plus 2,4-D mixture did not influence the control of wild oats obtained with any herbicide, indicating that the antagonism was due to the 2,4-D component of the picloram plus 2,4-D mixture.

Effects of temperature and interference were examined in a replacement series experiment with cotton (Gossypium hirsutum L. 'Stoneville 213′), spurred anoda Anoda cristata (L.) Schlecht. # ANVCR), and velvetleaf (Abutilon theophrasti Medic. # ABUTH). Plants were grown in controlled-environment greenhouses at day/night temperatures of 32/23 or 26/17 C, and harvested 14 or 39 days after planting. Height, dry weight, and leaf area at both harvests, and dry matter production and leaf area duration for the harvest interval were significantly greater in all species at 32/23 C than at 26/17 C. Interference reduced the dry weight per plant and leaf area at day 39, and dry matter production for the harvest interval. Cotton was somewhat superior to both weeds as a competitor at 32/23 C, while spurred anoda was somewhat superior to cotton and velvetleaf at 26/17 C.

Simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] inhibited photosynthesis 50% at concentrations of 1.1 μM for Spirogyra jurgensii (Kutz), 3.0 μM for Pithophora oedogonia (Mont.) Wittr., and 3.8 μM for Cladophora glomerata (L.) Kutz. Photosynthesis of Ankistrodesmus braunii (Brun.), a nonfilamentous species, was inhibited the same amount by 4.7 μM simazine. The filamentous algal species had significant reductions in growth but no other phytotoxic symptoms when exposed to 5 μM simazine at light intensities of 100 μE·m–2·s–1 and below. Algicidal effects did occur at a light intensity of 400 μE·m–2·s–1 and were most severe in Spirogyra. The relationship between light intensity and simazine toxicity indicates algicidal effectiveness on these filamentous algae will be limited in habitats where light is reduced by turbidity, depth, or self-shading.